The main factor limiting the performance of existing thermal imaging devices is the thermal conductance between adjacent pyroelectric elements and between each pyroelectric element and the supporting and interrogating structure.
In U.S. Pat. No. 4,354,109 there is disclosed a thermal imaging device incorporating an array of spaced apart pyroelectric elements in which each pyroelectric element is supported on a respective pillar formed from an epoxy resin containing an electrically conductive agent such as silver. Each pillar creates an electrical connection between the supported pyroelectric element and an integrated circuit effective to process electrical signals from the elements of the array, whilst also thermally insulating the element from the integrated circuit.
Such a device suffers the disadvantage however that the process for producing the pillars is relatively complicated, involving depositing a layer of the epoxy resin containing the electrically conductive agent, then ion beam milling the layer or machining the layer using optical cutting equipment or the like to create islands of the conductive epoxy material which may then be bonded to the pyroelectric elements and the integrated circuit.
The device described in U.S. Pat. No. 4,354,109 suffers the additional disadvantage that in order to achieve an adequate electrical path between the elements and the integrated circuit it is necessary to load the epoxy resin with sufficient effect of the pillars is limited. U.S. Pat. No. 4,354,109 quotes a value for the thermal conductivity of the pillars of 6 watts per centimeter degrees K., a value which would be inadequate in a practical imaging device.